Class: EM::Voldemort::Router

Inherits:
Object
  • Object
show all
Defined in:
lib/em-voldemort/router.rb

Overview

For a given request, the router figures out which partition on which node in the cluster it should be sent to. Ruby port of voldemort.routing.ConsistentRoutingStrategy.

Instance Method Summary collapse

Constructor Details

#initialize(type, replicas) ⇒ Router

Returns a new instance of Router.

Raises:



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# File 'lib/em-voldemort/router.rb', line 6

def initialize(type, replicas)
  raise ClientError, "unsupported routing strategy: #{type}" if !type && type != 'consistent-routing'
  raise ClientError, "bad number of replicas: #{replicas.inspect}" if !replicas || replicas <= 0
  @replicas = replicas
end

Instance Method Details

#partitions(key, partitions) ⇒ Object

Returns a list of partitions on which a particular key can be found.

Parameters:

  • key —

    A binary string

  • partitions —

    Hash of partition number to node



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# File 'lib/em-voldemort/router.rb', line 17

def partitions(key, partitions)
  master = fnv_hash(key) % partitions.size
  selected = [master]
  nodes = [partitions[master]]
  current = (master + 1) % partitions.size

  # Walk clockwise around the ring of partitions, starting from the master partition.
  # The next few unique nodes in ring order are the replicas.
  while current != master && selected.size < @replicas
    if !nodes.include? partitions[current]
      nodes << partitions[current]
      selected << current
    end
    current = (current + 1) % partitions.size
  end

  selected
end